In U.S. Pat. Application Ser. No. 359,533, filed May 11, 1973, and entitled "FLUID VALVE HAVING A PRESSURE RESPONSIVE INTERNAL MEMBRANE", now U.S. Pat. No. 3,844,529, there is disclosed what may properly be termed a pneumatic amplifier or a differential pressure transmitter valve. This disclosure will hereafter be referred to as the basic Brandt disclosure. As will become apparent from a reading and study of the Brandt disclosure, the particular valve thereof is designed to positively and linearly amplify pressure input signals. Generally reviewing the structure of the amplifier valve and how amplification is accomplished, it is seen from a study of this disclosure that the valve structure includes an open main internal chamber. Supported about the outer portions thereof by the valve structure and extending across said main internal chamber is an imperviable membrane member which effectively divides the internal main chamber into two compartments. The first compartment is designed to receive pressure input signals, while the second compartment is designed and adapted to receive and channel a supply air therethrough. Consequently, it is seen that the imperviable membrane member lies between two pressure systems. Essentially, amplification of input pressure signals, is accomplished by the response of the imperviable membrane member responding to the particular input pressure signal and restricting the flow of supply air through the valve structure. This restriction results in a pressure differential within the compartment within the valve structure channeling the supply air, the higher pressure of the pressure differential being a linear amplification of the input pressure signal.
It has been found that the gain of a particular amplifier valve is constant and is independent of the pressure signal applied and the flow rate of air passing through the valve. However, the principle problem lies in producing an amplifier valve that will yield a specific predetermined gain. In the basic Brandt disclosure referred to above, it was determined analytically that the gain of the amplifier valve shown therein could be varied by changing various valve parameters, particularly the radial demensions of the inner and outer seats. In attempting to producce an amplifier valve with a specific gain by controlling the parameters of the valve, it was found that such was difficult, if not nearly impossible, because of production limitations and other unconsidered factors that influence the gain.